Regulation of 5-HT2A/C receptors and DOI-induced behaviors by protein kinase Cgamma

Mechanical Regulation Underlies Effects of Exercise on Serotonin-Induced Signaling in the Prefrontal Cortex Neurons

Mechanical forces are known to be involved in various biological processes. However, it remains unclear whether brain functions are mechanically regulated under physiological conditions. Here, we demonstrate that treadmill running and passive head motion (PHM), both of which produce mechanical impact on the head, have similar effects on the hallucinogenic 5-hydroxytryptamine (5-HT) receptor subtype 2A (5-HT_2A) signaling in the prefrontal cortex (PFC) of rodents. PHM generates interstitial fluid movement that is estimated to exert shear stress of a few pascals on cells in the PFC. Fluid shear stress of a relevant magnitude on cultured neuronal cells induces ligand-independent internalization of 5-HT_2A receptor, which is observed in mouse PFC neurons after treadmill running or PHM. Furthermore, inhibition of interstitial fluid movement by introducing polyethylene glycol hydrogel eliminates the effect of PHM on 5-HT_2A receptor signaling in the PFC. Our findings indicate that neuronal cell function can be physiologically regulated by mechanical forces in the brain.

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Mechanical forces regulate brain functions under physiological conditions

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Intracerebral interstitial fluid has mechanical roles in regulating brain functions

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Mechanical impact on the head mediates effects of exercise on the brain

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Fluid shear stress physiologically modulates signaling in nervous cells

Protein Kinases Alter the Allosteric Modulation of the Serotonin Transporter In Vivo and In Vitro

AIM

Studies using S- and R-enantiomers of the SSRI citalopram have shown that R-citalopram exerts an antagonistic effect on the efficacy of the antidepressant S-citalopram (escitalopram) through an interaction at an allosteric modulator site on the serotonin transporter (SERT). Here, we show that protein kinase signaling systems are involved in the allosteric modulation of the SERT in vivo and in vitro.

METHODS

We assessed the effects of nonspecific protein kinase inhibitor staurosporine in the action of escitalopram and/or R-citalopram using electrophysiological and behavioral assays in rats and cell surface SERT expression measures in serotoninergic cells.

RESULTS

Acute administration of R-citalopram counteracted the escitalopram-induced suppression of the serotonin (5-HT) neuronal firing activity and increase of the head twitches number following L-5-hydroxytryptophan injection. Importantly, these counteracting effects of R-citalopram were abolished by prior systemic administration of staurosporine. Interestingly, the preventing effect of staurosporine on 5-HT neuronal firing activity was abolished by direct activation of protein kinase C with phorbol 12-myristate 13-acetate. Finally, in vitro, quantification of the amount of cell surface-expressed SERT molecules revealed that R-citalopram prevented escitalopram-induced SERT internalization that was completely altered by staurosporine.

CONCLUSION

Taken together, these results highlight for the first time an involvement of protein kinases in the allosteric modulation of SERT function.

Genetics and genomics of alcohol sensitivity

Alcohol abuse and alcoholism incur a heavy socioeconomic cost in many countries. Both genetic and environmental factors contribute to variation in the inebriating effects of alcohol and alcohol addiction among individuals within and across populations. From a genetics perspective, alcohol sensitivity is a quantitative trait determined by the cumulative effects of multiple segregating genes and their interactions with the environment. This review summarizes insights from model organisms as well as human populations that represent our current understanding of the genetic and genomic underpinnings that govern alcohol metabolism and the sedative and addictive effects of alcohol on the nervous system.

Head-twitch response in rodents induced by the hallucinogen 2,5-dimethoxy-4-iodoamphetamine: a comprehensive history, a re-evaluation of mechanisms, and its utility as a model

Two primary animal models persist for assessing hallucinogenic potential of novel compounds and for examining the pharmacological and neurobiological substrates underlying the actions of classical hallucinogens, the two-lever drug discrimination procedure and the drug-induced head-twitch response (HTR) in rodents. The substituted amphetamine hallucinogen, serotonin 2 (5-HT(2) ) receptor agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI) has emerged as the most popular pharmacological tool used in HTR studies of hallucinogens. Synthesizing classic, recent, and relatively overlooked findings, addressing ostensibly conflicting observations, and considering contemporary theories in receptor and behavioural pharmacology, this review provides an up-to-date and comprehensive synopsis of DOI and the HTR model, from neural mechanisms to utility for understanding psychiatric diseases. Also presented is support for the argument that, although both the two-lever drug discrimination and the HTR models in rodents are useful for uncovering receptors, interacting proteins, intracellular signalling pathways, and neurochemical processes affected by DOI and related classical hallucinogens, results from both models suggest they are not reporting hallucinogenic experiences in animals.

The genetic basis of alcoholism: multiple phenotypes, many genes, complex networks

Alcoholism is a significant public health problem. A picture of the genetic architecture underlying alcohol-related phenotypes is emerging from genome-wide association studies and work on genetically tractable model organisms.

Insights into the regulation of 5-HT2A serotonin receptors by scaffolding proteins and kinases

5-HT(2A) serotonin receptors are essential molecular targets for the actions of LSD-like hallucinogens and atypical antipsychotic drugs. 5-HT(2A) serotonin receptors also mediate a variety of physiological processes in peripheral and central nervous systems including platelet aggregation, smooth muscle contraction, and the modulation of mood and perception. Scaffolding proteins have emerged as important regulators of 5-HT(2A) receptors and our recent studies suggest multiple scaffolds exist for 5-HT(2A) receptors including PSD95, arrestin, and caveolin. In addition, a novel interaction has emerged between p90 ribosomal S6 kinase and 5-HT(2A) receptors which attenuates receptor signaling. This article reviews our recent studies and emphasizes the role of scaffolding proteins and kinases in the regulation of 5-HT(2A) trafficking, targeting and signaling.

Microarray analysis identifies cerebellar genes sensitive to chronic ethanol treatment in PKCgamma mice

Neuroadaptive changes that occur in the development of ethanol tolerance may be the result of alterations in gene expression. We have shown that PKCgamma wild-type mice develop tolerance to the sedative-hypnotic effects of ethanol after chronic ethanol treatment; whereas, mutant mice do not, making these genotypes a suitable model for identifying changes in gene expression related to tolerance development. Using a two-stage process, several genes were initially identified using microarray analyses of cerebellar tissue from ethanol-treated PKCgamma mutant and wild-type mice. Subsequent confirmation of a subset of these genes using quantitative real time reverse transcriptase polymerase chain reactions (qRT-PCR) was done to verify gene expression changes. A total of 109 genes from different functional classifications were identified in these groups on the microarrays. Eight genes were selected for verification as follows: three, Twik-1, Plp, and Adk2, were chosen as genes related to tolerance; another three, Hsp70.2, Bdnf, and Th, were chosen as genes related to resistance to tolerance; and two genes, JunB and Nur77, were selected as candidate genes sensitive to chronic ethanol. The results from the verification experiments indicated that Twik-1, which codes for a potassium channel, was associated with tolerance and appeared to be dependent on the presence of PKCgamma. No genes were confirmed to be related to resistance to tolerance; however, expression of two of these, Hsp70.2 and Th, were found to be sensitive to chronic ethanol and were added to the transcription factors, JunB and Nur77, confirmed by qRT-PCR, as a subset of genes that respond to chronic ethanol.